For millennia, the seas and other natural water reservoirs have provided an abundant and stable supply of sustenance. In recent years, however, overfishing, inefficient harvesting practices, and environmental stressors have resulted in the depletion or decline of certain fish populations in many regions. At the same time, an increasing human population, increasing standards of living, and an increasing awareness of the health benefits of seafood have increased the demand for fish and fish product.
Advances in aquaculture in general and fish farming in particular, as well as improvements in technology, have enabled significant progress to be made to efficiently address increasing world demand for fish product at lower costs. Developments in fish farming also reduce the risks associated with overfishing indigenous fish populations. In particular, offshore aquaculture systems, also known as open-ocean aquaculture, employing fish cages or fish pens, have found some success. Large, submersible fish pens suitable for aquaculture applications are known in the art to aid in the efficient and bio-responsible cultivation of food sources. In open-ocean aquaculture large fish pens are positioned some distance offshore, in deeper and less-sheltered waters, where ocean currents are relatively strong. The fish pens are stocked with young fish or fry, and the fish are fed and maintained until they reach maturity. The fish pens provide a habitat and protection for the fish. Similar fish pens may also be used for freshwater aquaculture, for example, in larger freshwater bodies of water.
A disadvantage of inshore aquaculture systems is that waste products from a fish farm can settle below the fish cage and accumulate on the seafloor, with potential adverse effects to the ecosystem of the benthic zone. By providing systems configured to retain the farm fish in offshore locations, the waste products are more rapidly swept away from the site and diluted. Offshore systems, away from more heavily trafficked inshore locations, are more readily sited and expanded to meet the increasing demands.
More recent innovations in fish pens employing a center spar buoy or center cluster of spar buoys are disclosed in U.S. Pat. No. 5,359,962, to Loverich, and in U.S. Pat. No. 5,617,813, to Loverich et al., both of which are hereby incorporated by reference in their entireties. Loverich et al. discloses a mobile pen for growing fish or shellfish wherein a central vertical spar buoy is surrounded by one or more horizontal rim assemblies. A mesh/netting extends from an upper end portion of the spar buoy outward to the rim assemblies, and then inward from the rim assembly to a lower end portion of the spar buoy. U.S. Pat. No. 9,072,282, to Madsen et al., which is also hereby incorporated by reference, discloses a spar buoy fish pen assembly with a deployable system for segregating a population of fish within a fish pen, and/or for crowding the fish into a smaller space, for example to facilitate treatment or harvesting operations.
There remains a need for improvements in fish pen construction. For example, in contained fish pen populations it is desirable to remove or separate sick or deceased fish from the healthy population quickly, in order to prevent harm to the healthy fish. In current fish pens it is difficult to isolate and remove deceased fish (“morts”) from the fish pen. It would be beneficial to isolate morts quickly, to maintain the health of the remaining population. It would also be beneficial to identify and remove morts quickly, to be able to determine the cause of death and, if appropriate, take corrective measures.